With the help of national rail expert Robert Comer, WLKY searched those reports, revealing a long list of chemicals quietly leaking and spilling from trains in Jefferson County since 1990.

"I thought it was shocking," said Comer. "The number of incidents I discovered in the national response center archives points to a very serious situation in Jefferson County."

With Comer's help, WLKY uncovered 270 incidents involving chemical releases on the rails of Jefferson County, almost 100 more than the 179 found upriver.

"Jefferson County had 33 percent more of these leaks of chemicals than Cincinnati, Ohio, and Hamilton County. It was kind of shocking, really," said Comer.

While dozens of the incidents note low-level risks like locomotives leaking oil or diesel fuel, the search of Jefferson County uncovered five spills or releases of calcium carbide, the key ingredient in acetylene torches.

The same material combined with water to burn workers led to a deadly plant explosion in Rubbertown in 2011.

In one case, it was noted a rail car started smoking due to the mixture of rain water and calcium carbide.

And WLKY found hydrochloric acid spilling or leaking from rail cars 32 times over the past 22 years, including a rail car that lost 33 percent of it's load of hydrochloric acid through a hole at the bottom of the car caused by corrosion.

Lots of other dangerous chemicals spilled, leaked or vented, too, including more than a dozen releases of butadiene, the same material that caught fire near West Point.

"It's amazing. It's outrageous," said Comer.

Comer said he is stunned by the list, not just because it proves dangerous chemicals are routinely being released, but because of a bigger threat posed by the faulty equipment, errors and other issues when those chemicals roll on rail cars through the heart of Louisville.

"The thing that's even more scary about it is that if one of these cars explodes or if one of these cars breaks open, you could have that chemical carried around by the wind, the air, not just around where the accident happened, but over the whole city," said Comer.

WLKY asked P&L Railway, which is at the center of the derailment, about hauling hazardous chemicals.

A spokesperson would only state "P&L transports federally designated hazardous materials under its obligation as a common carrier."

But one of the biggest rail companies that operates in Jefferson County had plenty to say.

In a written statement, Norfolk Southern's director of public relations wrote, "Norfolk Southern takes very seriously its role in transporting hazardous materials safely. In 2012 alone, we've spent $2.4 billion on capital expenditures, most of which goes to ensure that our track and equipment are maintained to the highest standards to ensure safe operations."